1. Field of the Invention
The present invention relates to the transfer of unsymmetrical products between points wherein the product orientation may be selectively changed during such movement, and particularly to the conveying of printing works products in such a manner that alternate products moving in a conveying direction may be rotated by 180.degree.. More specifically, this invention is directed to apparatus for selectively rotating printing works products, serially received on a conveyor, through an angle of 180.degree. and especially to a conveyor having a rotation station which clamps and arrests the movement of incoming products, imparts a desired rotation to the claimed products and thereafter accelerates the reoriented products in a conveying direction. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in connection with the manipulation, and particularly the stacking, of printing works products such as books, book blocks, brochures, stacks of sections of publications and stacks of book blocks. Printing works products of the types enumerated are characterized by a generally rectangular shape and a spine which extends along one edge. The spine region of such products is thicker than the oppositely disposed edge. Accordingly, in the stacking and palletizing of such printing works products, either individually or stack-by-stack, in order to compensate for spine slope and thus ensure stack stability, selective rotation of the products through an angle of 180.degree. is required. Typically, in the formation of stacks of the enumerated printing works products, the formed stacks will be comprised of products which are alternately rotated by 180.degree. relative to one another.
As an example of prior art apparatus for selectively rotating book blocks in the course of stacking the same, reference may be had to published German application No. 29 35 263. In the apparatus depicted in this published application, unbound book block sections are selectively rotated and then stacked. The apparatus for causing rotation is located between a feed conveyor and a discharge conveyor and is in the form of cooperating pairs of clamping plungers. These plunger pairs are associated with synchronized upper and lower conveyors. The plungers are spring biased so as to grip a product which is to be rotated in a central region thereof. The plungers are selectively rotatable through an angle of 180.degree. during movement with the associated conveyors. The lower plungers operate through the conveyor on which the product to be rotated is supported, the lower conveyor consisting of spaced belts. Acting in response to a rotation-control, the apparatus of the published German application enables books or book blocks to be fed to a downstream stacking mechanism, individually or stack-by-stack, with the spines of alternate in-fed products pointing in opposite directions.
The rotation device of German Application No. 29 35 263, with its multiplicity of controlled plungers mounted on separate continuously circulating chain drives, is an exceedingly complex mechanism which is characterized by relatively high cost and by volumetric inefficiency. Furthermore, as a result of sychronization difficulties, the alignment of the axes of cooperating upper and lower plungers cannot be maintained over a long working life. A misalignment of the plungers can result in the alignment of individual, or stacked, books or book blocks being lost. Any such misalignment is especially troublesome when the printing works product being handled comprises book sections which have been stacked but not yet bound to one another.
A further deficiency of prior art devices for selectively imparting rotation to printing works products resides in the fact that the control mechanisms therefor are complicated and expensive. Such control mechanisms must regulate the in-feed of the products from a hold-back stop on a feed conveyor to the point where the product is acquired by the rotation device, and such regulation must be able to take into account the necessity of acquiring products of different size and ensuring that each product, regardless of its size, is gripped so that it will be rotated about its center of gravity.